Device-to-Device Communications Underlaying Cellular Networks: To Use Unlicensed Spectrum or Not?

TL;DR

This paper explores the use of licensed and unlicensed spectrum for device-to-device communications underlaying cellular networks, proposing a stochastic geometry-based analysis and an SQP algorithm to optimize throughput.

Contribution

It introduces a stochastic geometry model for D2D and LTE spectrum sharing and develops a sequential quadratic programming algorithm for throughput maximization.

Findings

The analysis accurately predicts system throughput.

The proposed algorithm effectively improves spectrum utilization.

Simulation confirms the model's validity and algorithm's efficiency.

Abstract

In this paper, we consider device-to-device (D2D) communications as an underlay to the cellular networks over both licensed and unlicensed spectrum, where Long Term Evolution (LTE) users utilize the spectrum orthogonally while D2D users share the spectrum with LTE users. In the system, each LTE and D2D user can access the licensed or unlicensed band for communications. To maximize the total throughput of the system, we leverage stochastic geometry to derive the throughput for each kind of users by modeling the deployment of users as Poisson point processes (PPPs), and investigate the spectrum access problem for these users. Since the problem is NP-hard, we propose a sequential quadratic programming (SQP) based algorithm to obtain the corresponding suboptimal solutions. Theoretically, we evaluate the system performance by analyzing the throughput regions. Simulation results validate the accuracy of the geometric analysis and verify the effectiveness of the proposed algorithm.